Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B21/00—Nitrogen; Compounds thereof
  • C01B21/04—Purification or separation of nitrogen
  • C01B21/0405—Purification or separation processes
  • C01B21/0494—Combined chemical and physical processing
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
  • C21D1/76—Adjusting the composition of the atmosphere
  • C21D1/763—Adjusting the composition of the atmosphere using a catalyst
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0001—Separation or purification processing
  • C01B2210/0003—Chemical processing
  • C01B2210/0006—Chemical processing by reduction
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0001—Separation or purification processing
  • C01B2210/0009—Physical processing
  • C01B2210/001—Physical processing by making use of membranes
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B2210/00—Purification or separation of specific gases
  • C01B2210/0043—Impurity removed
  • C01B2210/0045—Oxygen
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/20—Capture or disposal of greenhouse gases of methane

Definitions

• the present invention relates to a process for heat treatment of metals in a furnace, under a heat treatment atmosphere formed by the addition of a gaseous stream of nitrogen with, where appropriate, one or more of the following constituents: hydrogen, methanol, hydrocarbon.
• composition of such heat treatment atmospheres must be substantially free of oxygen and generally admits the presence of water vapor only in relatively low contents, moreover defined from one application to another. This is the reason why, in the vast majority of applications of this type, one starts from very pure nitrogen produced by cryogenic distillation of the air, the residual oxygen content of which does not exceed 10 vpm (10 volumes per million). This so-called cryogenic nitrogen often has a high production cost, and therefore, in this heat treatment technique as in those using nitrogen or oxygen, we have been interested in other industrial sources. , in particular the separation of air by selective adsorption or permeation. The latter type of production is described in the document "Advanced Materials and Processes Volume 134 No. 3 Sept.
• cryogenic nitrogen these systems are not widespread because this high-purity nitrogen then leads to a production cost close to cryogenic nitrogen, while production plants by adsorption or permeation do not have the flexibility and simplicity of production facilities. of cryogenic nitrogen.
• the oxygen content of the raw nitrogen generator permeator is limited to 3%, this makes it possible to cover a certain number of applications in heat treatment which allow water vapor contents of up to 6%, as is the case with copper annealing or brazing, decarburizing annealing, nitriding of steel, or sintering of certain non-ferrous metals. If it is proposed to operate the permeator with a residual oxygen content of at least 0.5%, it is not only because wanting to improve the quality of separation of the permeator would lead to a cost price of nitrogen incompatible with the applications envisaged, but also because these applications require, or at least support without risk, water vapor contents at least equal to 1%.
• This nitrogen generator is of the selective membrane type.
• a semi-permeable membrane is used which can be in the form of hollow fibers to separate the compressed air into nitrogen and oxygen.
• a gas enriched in oxygen and water vapor is evacuated at the end of the separation module, while a dry gas enriched in nitrogen is on the side of the module.
• Such generators are well known and allow to generate a nitrogen gas whose purity varies from 97% to 99.5% depending on the setting made.
• the catalytic reaction requires the prior intervention of a mixer of crude nitrogen and hydrogen, advantageously associated with a buffer capacity.
• the catalyst is chosen so as to allow an immediate and complete reaction of the oxygen and this at room temperature, with a residual oxygen content of less than 30 vpm.
• the catalyst which can be used is of the alumina type with 0.5% of palladium which can treat an hourly flow rate of approximately 5000 to 10,000 times the volume of the reactor. This type of catalyst does not require any prior heating of the gas and, moreover, does not imply a reactor start-up sequence with initial release of gas into the open air.
• the treatment is usually carried out with cryogenic nitrogen and hydrogen (2 to 5%).
• cryogenic nitrogen With copper, it is imperative to have a very low residual oxygen content in the treatment gas to avoid oxidation problems.
• controlling the water vapor is not important.
• the cryogenic nitrogen is therefore advantageously replaced by a treatment gas from a permeation generator delivering crude nitrogen to which hydrogen is added such that there is 2 to 5% of hydrogen after catalytic reaction , this gaseous mixture containing water vapor, the amount of which is a function of the initial oxygen content in the nitrogen produced by the generator.
• cryogenic nitrogen is advantageously replaced by a treatment gas generated from a nitrogen generator by permeation to which hydrogen is added such that there is between 2 and 75% of hydrogen after catalytic reaction, the gas mixture containing water vapor, the content of which is a function of the initial oxygen content in the nitrogen.
• the nitriding treatments for steels can be carried out with nitrogen, ammonia (15 to 50%) and nitrous oxide 2 to 5%. These treatments are mainly carried out in batch ovens.
• the injection of nitrogen produced by a permeation generator could cause oxidation of the parts on cooling, this can be avoided by adding hydrogen in an amount just sufficient to ensure the catalytic transformation of oxygen into vapor of water.
• Cryogenic nitrogen is usually used with hydrogen to sinter these metals. It can advantageously be substituted with a mixture of permeation nitrogen and hydrogen such that there is 2 to 15% hydrogen after catalytic reaction.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Analytical Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Metallurgy (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Inorganic Chemistry (AREA)
• Separation Using Semi-Permeable Membranes (AREA)
• Powder Metallurgy (AREA)
• Catalysts (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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• 1988
  • 1988-11-24 FR FR8815323A patent/FR2639250B1/fr not_active Expired - Fee Related
• 1989
  • 1989-11-17 ES ES89403159T patent/ES2057166T3/es not_active Expired - Lifetime
  • 1989-11-17 EP EP89403159A patent/EP0375477B1/fr not_active Expired - Lifetime
  • 1989-11-17 DE DE68916925T patent/DE68916925T2/de not_active Expired - Fee Related
  • 1989-11-17 AT AT89403159T patent/ATE108752T1/de not_active IP Right Cessation
  • 1989-11-21 ZA ZA898876A patent/ZA898876B/xx unknown
  • 1989-11-21 CA CA002003473A patent/CA2003473A1/fr not_active Abandoned
  • 1989-11-24 PT PT92409A patent/PT92409B/pt not_active IP Right Cessation
  • 1989-11-24 AU AU45562/89A patent/AU630640B2/en not_active Ceased
  • 1989-11-24 JP JP1303437A patent/JPH07112925B2/ja not_active Expired - Lifetime

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